Add 32-bit libwinpthread-1.dll to windows toolchain dependencies.

Bug: http://b/34273721

  - Copy 32-bit libwinpthread-1.dll from
    prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8.
  - Corresponding build script change in a separate CL:
    https://android-review.googlesource.com/322278

Test: manually tested llvm-rs-cc.exe and bcc_compat.exe on windows.

Change-Id: Ib0c3f98734c68e174fd614f3940b706e25e945d7
(cherry picked from commit 5df9f20565e63906167c82f6120c78e969b3b467)
diff --git a/current/bin/libwinpthread-1.dll b/current/bin/libwinpthread-1.dll
new file mode 100755
index 0000000..94e343a
--- /dev/null
+++ b/current/bin/libwinpthread-1.dll
Binary files differ